I had the same problem with an old Scout 1110. I accidently lubed the inside of the housing that holds two plastic gears, which in turn hold the two springs and brushes down on the commutator. Oil even got down inside the brush holes onto the spinning face of the commutator. The engine would just hum, not run.
So, I opened everything back up, removed the two plastic gears, plus the brushes with springs, and two tiny copper leaf springs, and soaked them in 98% alcohol for 3 minutes. Then I totally dried them off. Then I completely swabbed out the inside of the housing with two or three Cue-Tips that were soaked in the alcohol, and used dried Cue-Tips to wipe them clean. Then I thrust a Cue-Tip soaked in alcohol down in the brush hole, so it was in contact with the commutator, and turned the engine wheels so that the contact area got totally wiped down. I did this with both brush holes. I used dry Cue-Tips down in the brush hole to remove the residue, again turning the engine wheels.
All of this took me about 15 minutes.
I then reassembled everything, and the Scout ran great, and much faster than before.
98% alcohol evaporates very fast. So it was not dripping around inside the motor.
Hope this helps.
Mannyrock
